Storms drive outgassing of CO2 in the subpolar Southern Ocean
Sarah Nicholson, Daniel Whitt, Ilker Fer, Marcel du Plessis, Alice Lebehot, Sebastiaan Swart, Adrienne J. Sutton, Pedro M. S. Monteiro
Abstract
Abstract The subpolar Southern Ocean is a critical region where CO 2 outgassing influences the global mean air-sea CO 2 flux (F CO2 ). However, the processes controlling the outgassing remain elusive. We show, using a multi-glider dataset combining F CO2 and ocean turbulence, that the air-sea gradient of CO 2 (∆pCO 2 ) is modulated by synoptic storm-driven ocean variability (20 µatm, 1–10 days) through two processes. Ekman transport explains 60% of the variability, and entrainment drives strong episodic CO 2 outgassing events of 2–4 mol m −2 yr −1 . Extrapolation across the subpolar Southern Ocean using a process model shows how ocean fronts spatially modulate synoptic variability in ∆pCO 2 (6 µatm 2 average) and how spatial variations in stratification influence synoptic entrainment of deeper carbon into the mixed layer (3.5 mol m −2 yr −1 average). These results not only constrain aliased-driven uncertainties in F CO2 but also the effects of synoptic variability on slower seasonal or longer ocean physics-carbon dynamics.